The invention relates to a grinding device comprising a housing and motor-driven drive shaft passing through a bearing unit with its free end extending from the housing, wherein at the free end of the drive shaft a tool receptacle is provided for the removable attachment of a tool and an enclosing suction hood abuts at the housing and surrounds the free end of the drive shaft, said hood having a suction space facing the tool receptacle.
Grinding devices of the type described above are used when working a surface using a motor-driven drive shaft, wherein a tool receptacle for removable attachment of a tool, particularly a grinding wheel, is disposed at its free end. Removed particles occur during a grinding operation by the rotary motion of the tool abrasively on the surface of the workpiece, said particles resulting in the development of a heavy dust. A suction hood is arranged on the housing of the grinding device to prevent or at least reduce contamination of the surroundings. The suction hood surrounds the free end of the tool receptacle and comprises a suction space facing the tool receptacle.
DE 195 03 201 A1 discloses a grinding device comprising a housing and a motor-driven drive shaft passing through a bearing unit and projecting from the housing at its free end. A tool receptacle is provided at the free end of the drive shaft for removably fastening a tool. An enclosing suction hood abuts at the housing enclosing the free end of the drive shaft. The hood has a suction space facing towards the tool receptacle. The bearing unit is protected by a seal against the incursion of dust.
The drawbacks of the known solution are that the sealing of the bearing unit is very costly and an incursion of dust into the bearing unit is not preventable.
The object of the present invention is to provide a grinding device that is economical to manufacture, that efficiently suctions off dust and prevents an incursion of dust into the bearing unit.
This object is achieved by the invention, wherein the suction space comprises a separator wall between the tool receptacle and the bearing unit that divides the suction space into a dirty space openly configured towards the tool receptacle and an adjacent drive space opposite to the tool receptacle. The separator wall comprises a through passage for passage of the drive shaft.
Since the suction space has a separator wall that separates the dust-sensitive parts, such as the bearing unit, from the dust, contamination of the parts by dust is prevented by a simple means, the separator wall.
Preferably, the dirty space comprises at least one discharge opening that is connectable to a source of underpressure [viz. vacuum]. By generating an underpressure in the dirty space, dust incursion into the driver space is prevented entirely since there is an overpressure in the driver space compared with the dirty space.
The driver space comprises at least one inlet opening that is open to the outside to assure an optimal supply of air from the surroundings of the grinding device. In a further embodiment of the invention, the inlet opening comprises an air filter, for example, for filtering dust from the air brought in from the outside.
A clearance is advantageously provided between the inner contour of the passage opening and the external contour of the drive shaft to avoid a seizing up of the drive shaft. Furthermore, the clearance enables an air current between the driver space and the dirty space. The clearance consequently prevents an incursion of dust through the through passage since, in that zone, the stream velocity is very high due to the pressure difference between the drive space and the dirty space.